During the first year of the proposed project, we have embarked upon the structure elucidation of protein and peptide inhibitors of calcium phosphate precipitation in human saliva as well as saliva of other species. To date we have completed the primary structure of statherin and most potent, and smallest, of the four anionic proline-rich proteins (PRP) in human saliva and have begun sequence determination of the protein inhibitors of calcium phosphate precipitation in saliva of other species as a first step comparative structural studies. An anionic proline-rich (PRP-like) protein and a statherin-like peptide from saliva of Macaca Arctoides have been highly purified. We have carried out NH2-terminal sequence analysis and have purified and partially sequenced the maleoylated tryptic peptides of the PRP-like protein from Macaca Arctoides, and we are presently initiating structural analysis on the statherin-like peptide. Finally we have extended our comparative structural studies by looking for inhibitors of calcium phosphate precipitation in the saliva of venomous and non-venomous snakes and other species phylogenetically distant from man. In addition to these comparative structural studies, we have begun localizing the site of precipitation-inhibition in the salivary phosphoproteins. We have demonstrated that the NH2-terminal tryptic peptides of all four anionic proline-rich proteins from human saliva contain the active regions necessary for calcium phosphate precipitation-inhibition and have purified and characterized on active collaginase fragment of statherin. Presently we are beginning synthetic studies to accurately define the active regions of these molecules and to determine minimal peptide chain lengths required for activity.